An apparatus and method for identifying the presence of high conductivity or permittivity conditions in a wide range of electrically insulating materials is disclosed. The apparatus includes a grounded enclosure containing electronics for controlling measurement and communication processes and first and second spaced-apart electrode assemblies for engaging an insulator to be tested. The first and second electrode assemblies are mounted in the enclosure for linear movement such that pressing of the first and second electrodes against an insulator causes the electronics to initiate a measurement.
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1. An apparatus for identifying high risk insulators with conductive or high permittivity defects, comprising:
(a) a metallic enclosure containing a microprocessor configured to control measurement and communication processes; and
(b) first and second spaced-apart electrode assemblies, each including an exposed electrode configured to engage an insulator to be tested, the first and second electrode assemblies being mounted to the enclosure for linear movement between first and second positions, the microprocessor programmed to initiate a measurement from a probe mounted on one of the exposed electrodes in response to movement of the first and second electrode assemblies to the second position.
17. A method of evaluating insulators for defects, comprising the steps of:
(a) providing an apparatus for identifying high risk insulators, the apparatus including:
(i) a microprocessor;
(ii) a high voltage electrode assembly; and
(iii) a grounded electrode assembly;
(b) adjusting the high voltage electrode assembly and grounded electrode assembly to obtain a desired spacing;
(c) calibrating the apparatus to provide a calibration result set for comparison with measurements taken on an insulator;
(d) engaging the high voltage electrode assembly and grounded electrode assembly with an insulator to be tested;
(e) submitting the insulator to a high voltage at various frequencies to determine a resonance frequency of the insulator;
(f) submitting the insulator to a high voltage at the resonance frequency for a pre-determined amount of time; and
(g) conducting measurements during the pre-determined amount of time for comparison to a the calibration result set.
13. An apparatus for identifying high risk insulators with conductive or high permittivity defects, comprising:
(a) a chassis having a plurality of apertures and first and second rails;
(b) a microprocessor mounted to the chassis for controlling measurement and communication processes;
(c) a high voltage electrode assembly connected to the chassis by a spring loaded mechanism to allow the high voltage electrode assembly to move linearly in and out from the chassis;
(d) a grounded electrode assembly connected to the chassis by a moveable plate and to the moveable plate by a spring loaded mechanism, the moveable plate adapted to move along the first and second rails to position the grounded electrode at a pre-determined spacing from the high voltage electrode assembly and the spring loaded mechanism adapted to allow the grounded electrode assembly to move linearly in and out from the chassis; and
(e) wherein when the high voltage electrode assembly and grounded electrode assembly are pushed against an insulator, the electrode assemblies move linearly inward towards the chassis, thereby causing the electronics to initiate a test.
2. The apparatus according to
3. The apparatus according to
4. The apparatus according to
5. The apparatus according to
6. The apparatus according to
7. The apparatus according to
(a) a metallic shaft for connecting the first electrode assembly to a chassis contained in the enclosure;
(b) a fiberglass rod connected to the metallic shaft; and
(c) a high voltage electrode connected to the fiberglass rod, wherein the fiberglass rod insulates the electrode from the metallic shaft.
8. The apparatus according to
(a) a metallic shaft configured to connect the second electrode assembly to a chassis contained in the enclosure; and
(b) a grounded electrode connected to the metallic shaft and electrically grounded to the chassis.
9. The apparatus according to
10. The apparatus according to
11. The apparatus according to
12. The apparatus according to
14. The apparatus according to
15. The apparatus according to
(a) a metallic shaft for connecting the high voltage electrode assembly to the spring loaded mechanism;
(b) a fiberglass rod connected to the metallic shaft; and
(c) a high voltage electrode connected to the fiberglass rod, wherein the fiberglass rod insulates the electrode from the metallic shaft.
16. The apparatus according to
(a) a metallic shaft for connecting the grounded electrode assembly to the moveable plate;
(b) a grounded electrode connected to the metallic shaft and electrically grounded to the chassis; and
(c) a sensing probe positioned in a cavity of the grounded electrode.
18. The method according to
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This application claims the benefit of Provisional Application No. 61/525,781 filed on Aug. 21, 2011.
This application relates to an apparatus and method for identifying the presence of high conductivity or permittivity conditions in a wide range of electrically insulating materials and, more particularly, to a detector to assess the electrical integrity of a polymer insulator.
Insulators are utilized in many applications on transmission and distribution systems. The main application of an insulator is to mechanically attach current carrying conductors to support grounded structures while electrically insulating the conductors from the grounded structures.
Non-ceramic insulators (NCI) (also called polymer or composite insulators) are considered high risk if they contain internal or external defects of conductive or high permittivity. An example of a conductive defect would include internal carbonization of the fiberglass rod due to discharge activity, and an example of a high permittivity defect would be water internal to the insulator.
A requirement for ensuring worker safety when performing live work (LW) with polymer insulators is to confirm the short-term (i.e. for the duration of the work) electrical and mechanical integrity of both the installed and the replacement polymer units. Currently there are no generally accepted and easily applied procedures to accomplish this. Consequently, some utilities have opted not to use polymer insulators. In addition, a number of utilities that do use polymer insulators avoid live work on structures on which these insulators have been installed.
Accordingly, there is a need for an apparatus and method that can identify electrical and mechanical integrity of both installed and replacement polymer insulators.
These and other shortcomings of the prior art are addressed by the present invention, which provides an apparatus for identifying high risk insulators with conductive or high permittivity defects. The apparatus includes a metallic enclosure containing electronics for controlling measurement and communication processes, and first and second spaced-apart electrode assemblies for engaging an insulator to be tested. The first and second electrode assemblies are mounted in the enclosure for linear movement such that pressing of the first and second electrodes against an insulator causes the electronics to initiate a measurement.
According to an aspect of the invention, an apparatus for identifying high risk insulators with conductive or high permittivity defects includes a chassis having a plurality of apertures and first and second rails, electronics mounted to the metallic chassis which is electrically grounded to the metallic enclosure for controlling measurement and communication processes, a high voltage electrode assembly connected to the chassis by a spring loaded mechanism to allow the high voltage electrode assembly to move linearly in and out from the chassis, and a grounded electrode assembly connected to the metallic chassis by a moveable plate and to the moveable plate by a spring loaded mechanism. The moveable plate is adapted to move along the first and second rails to position the grounded electrode at a pre-determined spacing from the high voltage electrode assembly and the spring loaded mechanism is adapted to allow the grounded electrode assembly to move linearly in and out from the chassis. When the high voltage electrode assembly and grounded electrode assembly are pushed against an insulator, the electrode assemblies move linearly inward towards the chassis, thereby causing the electronics to initiate a test.
According to another aspect of the invention, a method of evaluating insulators for defects includes the steps of providing an apparatus for identifying high risk insulators having a microprocessor, a high voltage electrode assembly, and a grounded electrode assembly. The method further includes the steps of engaging the high voltage electrode assembly and grounded electrode assembly with an insulator to be tested, submitting the insulator to a high voltage at various frequencies to determine a resonance frequency of the insulator, submitting the insulator to a high voltage at the resonance frequency for a pre-determined amount of time, and conducting measurements during the pre-determined amount of time for comparison to a calibration result set.
The subject matter that is regarded as the invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:
FIGS. 8 and 9A-9C show electrode assemblies of the apparatus of
Referring to the drawings, an exemplary apparatus in form of a detector according to an embodiment of the invention is illustrated in
The detector 10 has the capacity to identify conductive, semi-conductive or high permittivity conditions, both internal and external without physical contact with internal conductive defects. The detector 10 is able to identify conductive, semi-conductive and high permittivity internal conditions which occur in service and are small in dimension electrically.
The detector 10 is portable, self-contained, lightweight, able to be used on energized installed insulators, may be installed on the end of a “hotstick” (
As shown, the detector 10 includes a Faraday cage 11 (also called a guard electrode), a tuning forks 12 and 13, bunny ears 14 and 15, a grounded enclosure 16, a universal hotstick receiver 17, a high voltage electrode assembly 18, and a grounded electrode assembly 19. The cage 11 houses the enclosure 16 and ensures that measurements taken by the detector 10 are not impacted by the presence of nearby conductive objects. The cage 11 also reduces high electric field and arcing effects on the detector 10 when it is in energized environments. The enclosure 16 may be bonded to the cage 11 or floating with respect to the cage 11. As shown, the enclosure 16 is floating and houses all of the electronics needed for the detector 10 to operate, including circuit boards, batteries, and power supplies to shield the electronics from electrical disturbances, electric fields, and arcing.
The tuning forks 12, 13 and bunny ears 14, 15 extend the Faraday cage 11 around the electrode assemblies 18 and 19. The tuning forks 12 and 13 are designed such that they make mechanical and electrical contact with end fittings of an insulator (
The receiver 17 is connected to the enclosure 16 and is bonded to the cage 11. The receiver 17 is adapted to receive and connect to a hotstick to allow the detector 10 to be placed on an energized insulator. The receiver 17 includes a slot 20 for receiving a connector of a hotstick and a plurality of blocks 21 to form a castellated end 22 that meshes with a castellated end of the hotstick, thereby preventing the detector from rotating with respect to the hotstick during installation. The castellated end 22 also allows the hotstick to be secured to the detector 10 at various angles relative to the hotstick to allow for easier installation.
Referring to
To move the plate 30 along the rails 31 and 32 and adjust the distance between electrode assemblies 18 and 19, a user pulls on a handle 36 of the connector 33 which moves the pin against the bias of the spring and disengages the pin from an aperture 34 of the chassis 29 to allow the plate 30 to move. Once the plate 30 and electrode 19 is in position, the user releases the handle 36 and the spring forces the pin into an aperture 34 of the chassis 29.
Micro-switches 38 and 38′ are also attached to the chassis 29 and are operably connected to the electrode assemblies 18 and 19 and electrically attached to electronics 39 to tell the electronics 39,
Referring to
As illustrated in
Referring to
Once the detector is engaged, a high voltage resonant voltage supply 61 sweeps through a frequency range and determines the resonance of the insulator. A high voltage at the resonant frequency is then supplied for a pre-determined amount of time, for example, 10 seconds. During this time, the current in HV supply, the drive level from power electronics to supply, the resonant frequency, and the measurements from sensing probes 50 are measured. The results are then compared against the “calibration” values. Depending whether the results are within some “predefined band” from the initial calibration, LED 57 or LED 58 is provided to the user. The results may also be sent to an RF enabled wireless device and/or via buzzer 59. Through the measurement process the buzzer 59 sounds so that the user knows a measurement is being made. The high voltage supply 61 is a custom high frequency (in the implementation 1-2 MHZ) high voltage supply (in the implementation 1-3 kV) that uses a custom ferrite transformer and power electronics to create the voltage.
The RF receiver 56 allows the unit to be remotely controlled and to provide results to an RF enabled device. In the implementation, WiFi is used and the device hosts an HTML interface (web page) which allows a laptop, phone or tablet to control the device and report results. This option is not always used—the user may also simply use LEDs 40, 41, 57, 58 together with the buzzer 59.
The detector 10 may also be battery powered. The battery may be rechargeable, such as a special lithium polymer battery which requires special charging. The electronics 39 contain charging intelligence and is capable of receiving power from an 8-14V DC source, e.g. from a car.
In operation, a test sequence is initiated by either the operator pushing the electrodes against the insulator or a remote RF enabled device (in this case any WiFi enabled computer, phone or tablet). A high frequency (in the implementation 1-2 MHZ) high voltage (in the implementation 1-3 kV) is placed across a section of the insulator, and the sensing probe 50 integrated into the grounded electrode 43′ measures the capacitive and resistive currents. LED 57 indicates whether there is a condition based on (a) the sensing probe measurement, (b) the current drawn by the high voltage supply 61, and (c) the resonant frequency of the high voltage supply. LED 41 provides an indication of any erroneous measurement such as (a) the measurements do not fit the expected profile, (b) contact is lost with the insulator, (c) the on-board battery voltage is low, and (d) self diagnostics of the electronics. The remote RF enabled device also provides these indications plus more detailed information. It also keeps a history of the measurements and provides a graph of measurements along the insulator.
The foregoing has described an apparatus and method for identifying the presence of high conductivity or permittivity conditions in a wide range of electrically insulating materials. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention. Accordingly, the foregoing description of the preferred embodiment of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation.
Phillips, Andrew John, Major, Mark, Lynch, Robert Carlton, Beverly, Phillip Nathan, Harrell, Sam
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Aug 20 2012 | LYNCH, ROBERT CARLTON | Southwest Research Institute | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 029038 | /0082 | |
Aug 23 2012 | MAJOR, J MARK | Southwest Research Institute | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 029038 | /0045 | |
Aug 23 2012 | BEVERLY, PHILLIP N | Southwest Research Institute | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 029038 | /0045 | |
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Oct 23 2012 | PHILLIPS, ANDREW JOHN | Electric Power Research Institute, Inc | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 029255 | /0293 | |
Oct 24 2012 | HARRELL, SAM | Electric Power Research Institute, Inc | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 029255 | /0293 |
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